Telephone system.



PATENTED MAY 23, 1905.

J. G. ROBERTS. TELEPHONE SYSTEM.

0 APPLICATION FILED MAY 8, 1902 4 SHEETS-SHEET 1.

PATENTED MAY 23, 1905.

J.- G. ROBERTS.

TELEPHONE SYSTEM.

APPLIGALION FILED MAY 8, 1902.

4 SHEETS-SHEET 2.

PATENTED MAY 23, 1905.

J. G. ROBERTS.

TELEPHONE SYSTEM.

APPLIOATION FILED MAY 8, 1902.

4 SHEETS-SHEET 3.

PATENTED MAY 23, 1905.

J. G. ROBERTS.

TELEPHONE SYSTEM.

APPLIOATION FILED MAY 3, 1002.

f} SHEETS-SHEET 4.

lllllllllllllllll GI Mo/mwq.

J17. dmmm Patented May 23, 1905.

Fries.

PATENT JOHN G. ROBERTS, OF EVANSTON, ILLINOIS, ASSIGNOR TO KELLOGGSWITCHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS,

A CORPORATION OF ILLINOIS.

TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 790,854, dated May 23,1905.

Continuation of renewed application, Serial No. 48,590, filed February23, 1901. This application filed May 8, 1902, Serial No. 106,400.

1'0 all whom, it nuty concern:

Be it known that I, JOHN G. RoBuRTs, a citi-' My invention relates to acentral-office equipment in telephone-exchanges whereby substations maybe connected together with the least possible work by the operator; andit consists in automatic means for switching the operators set and thecalling-generator on and off the circuit at the proper moments duringthe process of making a complete connection; also, in means foroperating the signals for calling central and disconnecting and incertain other arrangements and combinations hereinafter specified.

The devices hereinafter described are ap- S pllcable to central energysystems of the usual type, and while more particularly adapted to thesystem of circuits herein described are not necessarily limited thereto.

In the drawings, Figure l is a diagram of one form of my invention. Fig.2 is a diagram of circuits of a multiple switchboard, showing twosubstations with lines to a signaling apparatus at the exchange and acordcircuit with supervisory signals whereby an operator may connect thetwo substations together and disconnect them when the subscribers arethrough talking. Fig. 3 illustrates the busy-test circuit. Fig. 4Lillustrates the circuits of a multiple switchboard, showing the twosubstations with connecting-lines, the signaling apparatus at theswitchboard, a cord-circuit with supervisory signals, and relay-circuitswhereby the switching necessary to enable the operator to listen in onthe line and to connect the generator onto the line to call thesubscriber are automatically made by putting up and taking downconnections. Figs. 5 and 6 illustrate the ringing-machine used, Fig. 5being a vertical elevation of the same and Fig. 6 being the left-handside view thereof.

Referring to Fig. 2, X and Y are subscribers stations, each furnishedwith a con' denser c and call-bell permanently in circuit between thelimbs of the line and a transmitter 25 and receiver '1" in a bridge ofthe line normally open at the switch-hook I. The two limbs M and L ofthese lines extend to the central office, where they are fitted withanswering-jacks D and multiple jacks D, the limb L leading directly tothe multiple-contact tip-springs (l of the several jacks, while theopposite limb M is connected with the common office ground or commonoflice-return G and with the grounded pole of the direct-currentgenerator A, as shown. The tipspring (Z of the answering-jack isconnected through a normal contact 2 with the winding 6 of the linevisual signal B and thence by conductor 2 with the back contact of thecutoff relay E, the armature of which relay is connected with lead D,extending to the live pole of the generator A. The sleeve-contacts ofthe jacks are connected in multiple and by means of conductor 2 with theaxis of the rotary target of the line-signal B. The winding 0 of thecut-off relay E is connected by conductor 2 with the normal contact 4 ofthe shutter or target 6 while its forward contact 5 is connecteddirectly with ground, the common ofiice-return, or with the lineconductor M, as shown.

The operators cord-circuit is supplied with an answering-plug H and acalling-plug H, the tip-contacts ll of which are connected together bythe strand 7t and the interposed condenser 0, while the sleeve-contactsit of the plugs are directly connected by strand h, which in turn isconnected with the grounded pole of the battery through conductor it. Asupervisory signal (4, having a visual indicator, is associated with theanswering-plug, and a similar signal a is associated with plug H. Thewindings of these signals are connected between the cord-strand [L3 oneach side of the condenser c and conductor D leading to the live pole ofthe generator A. A key K may be depressed to connect the operatorshead-telephone is with the cord-circuit, a condenser 0 and secondaryWinding of her induction-coil 70 being included in series therewithbetween the strand it at the right of condenser 0 and the lead D".Current for the operators transmitter 70 and the primary winding of herinduction-coil is preferably furnished by a battery is in a localcircuit. An alternating-current generator C serves to call thesubscribers from the central oflice, a key K serving to connect the samewith the cordcircuit.

Th-e'ope'ration is as follows: The subscriber X in taking up hisreceiver closes the circuit of the line through the telephoneinstruments and permitscurrent from the live poleof the generator A toflow over cond uctor D, armaturc,and back contact 3 of cut-off relay E,conductor 2", winding?) of line-relay 13, contact 2, tip-spring (Z ofjack D, limb L of the telephone lin e, through the telephone instrumentsat the substation and back to the central office over limb M to groundand dead pole of the generator A. The current in this path actuatesline-signal B, which exposes its target to indicate a call. The armatureof the signal B is normally in contact with a point at 4:, as stated;but when the coil is energized it partially rotates and makes contact at5. The sleeve d of the jack D is thus grounded through the line M or Gwhen the signal on that line is displayed. The operator seeing thesignal displayed answers the call by inserting'the plug H in the jack Dand depressing her key K to connect her telephone in circuit. The tip ofthe plug it when inserted in the jack lifts the spring d from contact 2,thus opening the circuit of the signal B, whereupon it is automaticallyrestored to the position shown. The sleeve h of the plug H beinggrounded through the conductors 71/ and h, the sleeve cl is alsogrounded and a circuit is formed through the coil 6 of the cut-ofi'relay E, said circuit being from the live pole-of generator- A, lead Dwinding 0, conductor 2, contact 4 of linesignal B, the target 6 of thesignal, conductor 2", jack contact cl, strand and branch 71, to ground,and dead pole of the generator A. This circuit could not be made withoutopening contact 20f the jack D after the signal is once displayed, forotherwise the contact in the signal B at 4 would be opened. Afterreceiving her instructions the operator tests Ys line with thecalling-plug H in the manner hereinafter stated. If it is not busy, theplug is inserted in any one of the multiple jacks D D and the subscriberwanted is called by the generator O in the usual way 'over a circuitfrom the live side of the generator Ca depressed key K, tip-strand 7L3,tip-spring cl of the multiple jack D line-limb L, through the condenserc, and the call-bell at the subscribers station Y, operating the saidcall-bell, and back over limb M to the central olfice and grounded poleof generator C Y The insertion of plug H in the jack D completes thecircuit through the coil 0 of the cut-off relay E through the sleeve hof the plug. The completion of this circuit energizes the winding of therelay E and causes it to attract its armature, thus breaking contact 3and opening the circuit through the coil of the signal B. The current tocharge the transmitters at stations X and Y is furnished from thegenerator A through the coils of supervisory signals a a, which signalsare displayed during the conversation and are restored when theircircuits are opened by the receivers being placed back upon their hooks,the weight of the receiver breaking the contact in the substation, andthus opening the circuit. These circuits may be traced from the liveside of the generator A, through signal a or a to the tip of thecorresponding plug, to jack-spring d, to limb L of the telephone-lines,through transmitter and receiver contact l and the hook, and back onlimb M to the grounded side of the generator A.

Inasmuch as the multiple jacks have precisely the same connections, thesame circuit exists to substation Y as to substation X and is opened byplacing the receiver-on the hook, thus breaking contact Z in the samemanner. Thus it will be seen that the lifting of the receiver by thesubscriber in the substation throws the signal at the central :officecorresponding to that line, providing a connection is not already madeby a plug in any of the jacks of that line,- and the insertion of theplug in the answering-jack restores the signal, but displays anoperators signal so long as the receiver is off from the hook. Onascertaining the number of the subscriber called for the operatorinserts the connecting or calling plug of a pair into a multiple jack ofthe called line. The operators signal belonging to the cord and of thepair thus engaged re mains undisplayed until the subscriber called [foranswers by removing his receiver from its hook, it remainingdisplayeduntil the receiver is replaced upon the hook. The restoration of thereceiver of either the called or calling subscriber'to its hook breaksthe circuit and restores the corresponding signal to its normalcondition. Itwill be understood that an operator will not insert aconnecting-plug in the multiple jack of a line at at-ime when the signalbelonging to that line'is displayed by the action of a callingsubscriber, as she-would be warned otf theline by the busy test, ashereinafter explained, unless she should chooseto insert the plug for apurpose, also hereinafter explained,

and wait for the not-busy signal when the wanted subscriber restores hisreceiver to its hook. During the lnterval occurring when a subscriberssignal is displayed, as-assumed,

the operators act of placing a plug in the corresponding multiple jackwould not restore the signal, because the circuit is at that time opento the coil of the cut-ofi relayE at contact 4. Fig. 1 shows in simplediagram this talking-circuit. The steady generator-current flows out tothe substations from thelive pole of generator A through the coils ofthe supervisory relays a and a and serves to charge the transmitters atthe substations for talking, the current finding its'way back to thecentral office and opposite pole of the generator either over aground-conductor or the line-limb M. The voice-currents travel over theouter rectangular path indicated, the condenser 0 permitting the passagethereof, while the coils a and a have suflicient impedance orself-induction to prevent their passage. The condenser 0, being opaqueto steady current, renders the supervisory signals a and a inclividualor selective in their operation.

Fig. 3 shows the test-circuit which would occur should the operator testYs line at the momentY was himself making a call for central and beforethe operator had answered. The operators listening-keyKis shown down,the tip of the calling-plug H is just touching the sleeve (Z of themultiple jack D and the signal B is displayed. The testing-circuit isclosed from the live pole of generator A through the operatorsinstruments, the tipstrand it, ti p-contact /L of the plug H, throughthe sleeve (Z of the jack D over conductor 2", through the armature ofthe signal B, and the contact 5, made by the signal-armature, and thenceto the grounded pole of the generator A. A surge of current through theoperators instrument to charge the condenser 0 will cause a click to beheard by the operator, warning her that the line is busy. The condenserc in the operators circuit may be shunted by a high resistance to makethis test plainly audible, although it is notv absolutely necessary. Thesame test would occur to the operator if instead of the signal B beingdisplayed another plug was inserted in another jack on the line, for thetest-ring of the jack would then be connected to the ground or dead sideof the generator by the sleevestrand and conductor 71; of that plug, asseen in Fig. 2. If the line is not in use, the operator will not get aclick on testing the line, for with the signal B down and no other plugin a jack on the line neither the generator A nor any part of it isincluded in the test-circuit when an operator is making a test on theline, or, in other words, the test-rings of the jacks are not grounded.

Fig. 4 is another diagram of circuits of a multipleswitchboard andapparatus embodying the same principle and showing two substations withlines to the central office and signaling apparatus to the switchboardand a .cord-circuit with supervisory signals and relay-circuits wherebythe switching necessary for the generator to be connected to the line tocall the subscriber are automatically made without any other operationsthan those of plugging into and taking the plug out of the jacks of theline.

The line-circuits and apparatus are substantially the same as thosedescribed in Fig. 2. The line-signal B, however, is replaced by a relayB, and the supervisory signals are replaced by relays A. and N Thetalking-circuit in Fig. 4 is the same as that in Fig. 2 and Fig. 1. Theline and supervisory signals in Fig. 4 are shown as incandescent lamps AA A, and A but may be of the needle, shutter, or any other type, asdescribed. A is a generator to supply direct current to the relays B, B,and A, and N and is of high enough electromotive force to supply currentfor the transmitters at the substations through the coils of the relaysA and N". B is also a direct-current generator to supply current to thecoils of the cut-off relays E E, the starting-magnet N of theringing-machine R, and the lamp-signals A A A A. The generator B ispreferably of a lower electromotive force than generator A to save wireon the relays and make the resistance of these local circuits lower; butit is not necessarily a separate generator from A. In fact, generator Bcould be dispensed with and then the common generator line or lead Dwould. be connected to or form a part of the ground-line G. It isconvenient, however. Hence I have shown it in the diagram. This speciesof my invention in which I employ a single generator A is shown,described, and claimed by me in my divisional application, Serial No.95,155, filed February 24:, 1902. is the alternating-current generatorused for calling the subscribers to their telephones. Ris theringing-machine, which is shown in Figs. 5 and 6, and N, N, and N arerelays, the functions of which will appear later in the description of.the operation of the system.

Referring to Fig. A, the operation of this system is as follows: X callscentral by removing his receiver from its hook, thus closing his line atcontact Z through the coil of the line-relay B and generator A at theswitchboard, as before described, which relay in turn closes contact 9through the line-signal A and generator B The armature of relay B, whichis normally on contact 10, connected with the common generator-wire D*,is now in connection through contact 9 with the common generator-wire D.The jack-sleeves on that line are now all in condition to test busy.that is, in this construction the operator testing the line in any ofits multiple jacks will get the busy-test click in her telephone. Thisarrangement for a test is the same as de.

scribed in the circuit in Fig. 3, except that the test-rings are nowconnected with the neg.-

ative pole of generator B instead of with &

tor seeing the signal A displayed inserts an answering-plug H of thecord-circuit in the answering-jack D of that line and in doing so opensthe contact 2, restoring the relay B, thereby opening contact 9,restoring contact 10, and short-circuiting and extinguishing theline-signal A A circuit is now formed by the contact between the tip 7bof the plug H and the spring cl of the jack D from the generator A,through conductor 7?, the coil of supervisory relay A, opening itsnormally closed contact 11 and tip-strand it out over the limb L of thetelephone-line to substation X, thence through the transmitter t andreceiver 9, back over limb M to ground G and generator A at the centraloffice. A circuit is also formed from the generator B through conductor706, the coil of the supervisory relay N closing both its normally opencontacts 12 and 13 through strand [1,2 and the contact between thesleeves h of the plug H and (Z of the jack D, through the coil 6 ofrelay E, thus opening its normally closed contact 3, included in thenormal circuit of relay B, thence around the shunt of the lamp A formedby the armature and contact 10 of line-relay B, and back on common wireD to the opposite pole of generator B The opening of the contact 11prevents the supervisory signal A from being displayed, although thecontact at 12 is made. The contact made at 13 switches the operatorshead-phone circuit, one terminal of which is connected to lead D in thecord-circuit D The operator immediately answers the call in the usualway and receives her instructions from X. Learning that X wishes to talkto Y, the operator picks up the calling-plug H and proceeds in the usualway to test Ys line by the jack D which is the jack on Ys line that iswithin her reach. 1n touching the tip it of the plug H to the sleeve dof the jack D she will, if the line is not busy, hear no click in herear, the sleeve of the jack being connected with the same pole of thegenerator, and therefore at the same potential as the tip of her. plug,whereby no current can pass through her headphone. She then plugs H intojack D the signal A being immediately displayed, as later explained, andremains so until Y answers the call or until the plug H is removed fromthe jack D, as will be explained. At the moment the sleeve h of the plugH makes contact with the sleeve (Z of the jack D acircuit from thenegative pole of generator B is formed through wire W, the coil ofsupervisory relay N opening the normally closed contact 14, thus cuttingout the operators head-phone circuit and closing the normally opencontact 15, thence through the cordstrand W to plug H, then through thecoil 6 of the cut-off relay E, opening its normally closed contact 3 inthe circuit of the line-signal relay B, then through the shunt of lamp Aincluding the armature and the back contact 10 of line-relay B, tothecommon wire D, and back to the positive pole of generator B Theclosing of contact 15 forms a circuit from the generator B throughcontact 15, then through the signal A and causing it to be displayed,then through the normally closed contact 16 of the relay N through thewire V and D, back to B The relay N remains inoperative on account ofthe condenser c at Ys instrument, which opens the circuit at that pointand the condenser c in strand lb The closing of the contact 15 formsanother circuit from the generator B followingthe same path as the otherone to contact 15 and then through the wire W the normally closedcontact 20 of the relay N*, the wire W, and through the coil of themagnet N, starting the ringing mechanism R, as previously referred toand shown in detail in Figs. 5 and 6, then through the Wire W to contact16 of relay N and through wire V, back on common wire D to the otherside of B. As the cam S of the ringing mechanism revolves, ashereinafter explained, during the energization of the starting-relay Ncontact 23 is made and broken alternately, contact 22 being open whencontact 23 is closed and closed when 23 is open. The alternatingcurrentgenerator C is consequently switched on and off Ys line at contact 23and rings his bell accordingly through the condenser 0 at the substationand the ringing-circuit being the same as that described in Fig. 2. Assoon as Y removes his receiver from its hook to answer the call and ifat that moment contact 22 is closed, or as soon thereafter as it isclosed, current will pass from generator A, over wire V, through thecoil of relay N opening contact 16 and closing contact 17, then throughcontact 22 in R, then to the tip it of the plug H and spring (Z of thejack D to limb L of the line, through the telephone instruments at Y,and back to the wire M and ground-wire G to the opposite side of generator A. The opening of contact 16 opens the circuit to and extinguishesthe supervisory signal A and also opens the circuit of the coil of thecontrolling-magnet N of the ringing mechanism R, causing the gear S andcam S to revolve back to their normal position, as will be hereinafterexplained. The contact 17 made by the armature of relayi formsa circuitfrom generator B through contact15, wire VV .the coil of relay N",closing contact 21 and opening contact 20, then through contact 17 andback on wire V and common wire D to generator B. 20 opens the circuit ofcurrent-supply to starting or ringing magnet N, as well as does the opencontact 16. The closing of contact 21 closes the circuit ofcurrent-supply to the coil of relay N" in a parallel path to the contactat 17 so that the circuit through the coil of relay 1 4 is locked andcannot be opened again until the plug H is removed from jack D Theopening of contact and by so doing opening the circuit through the coilof the relay N, which opens its contact 15. If, however, Y does notanswer the call, the ringing mechanism will be automatically releasedwhen the stop S carried by the wheel S revolves around to point S andgrounds the relay 1 as hereinafter described, the current passing fromgenerator A through the coil of N to strip S and from there to stop Sand to ground-line G- and back to A at the moment of contact between Sand S. The result is the same as regards the operation of relay N andmagnet N 5 as would be had if Y had raised his receiver from the hook.The relay-armatu re of relay N having closed contact 17 for a moment,almostimmediately falls back again, for contact 5 is instantly openedand the groundline G connection removed by the ringingmachine revolvingback to its normal position, the mechanism for accomplishing which willbe fully described. The contact at 21, however, has been closed by thisaction of relay N and contact 20 opened, so that current is securely cutoff from the magnet-coil N Now assuming that Y had answered his call, asbefore mentioned, and is through talking, he replaces his receiver onits hook, thus opening the circuit through his telephone at the switch,current is cut off at that point from the relay 1 contact 17 is opened,and contact at 16 is closed and the signal A is displayed to theoperator through the same circuit as previously traced when plug H isfirst inserted in jack D thus informing the operator that Y has replacedhis receiver on the hook. For the same reason as before stated theopening of this contact 17 does not now cut 011' current from the coilof relay N, because the parallel contact 21 remains closed and locks thecircuit. In the same manner subscriber X on replacing his receiver onits hook opens the circuit through the coil of the supervisory relay A,releasing its armature, closing its contact, and displaying thesupervisory signal A*, current passing from generator B, over wire It,through contact 12,

signal A, the back contact of relay A, and

wire it, back to common wire D and generator B The two signals A and Abeing displayed, the operator knows that the conversation is terminated.1t is then her duty to disconnect, which she does by removing plug Hfrom jack D and plug H from jack D which cuts off current from relay N,opening contact 12 and extinguishing the signal A; likewise from relayN, closing contact 1 1 and opening contact 15. The opening of contact 15cuts current 05 from and extinguishes the signal A and also cuts offcurrent from the coil of the relay N closing contact 20 and openingcontact 21. Current is also cut off from relay E, which closes itscontact 3, and the removal of the plug H closes the contact in the jackD. The disconnection is now complete, current is cut off from allrelay-coils and the ringing-coil, and all parts and contacts are intheir normal positions.

To explain the busy test: Suppose the operator to be testing Ys line atjack 1) with plug H just after Y had raised his receiver from the hookand before Ys operator had answered the call. The operator would get aclick in her car from current from the generator B passing through herhead-phone, contacts 14 and 13 to D, then through tipstrand 7L3 andcontact 22, thence to the tip of plug H, to the sleeve d of jack Dthrough the coil 6 of relay E to the armature of relay B and its forwardcontact 9, and back through wire \V" to common wire I) and to the otherpole of generator B Now suppose Y had called central and Ys operator hadanswered the call by placing a plug in the answering-jack D, orsupposing any operator on any board had placed a callingplug in anyother multiple jack, the sleeves of all the jacks on Ys line would be inconnection with the common wire D through the relay-coils, such as N orN, of another cord-circuit corresponding to those shown in Fig. 4.Consequently an operator testing the line during that time will get aclick in her ear from current passing through her headphone from thegenerator B in a similar manner to that described above.

Should the operator be unable to get Y to the phone, she will be madeaware of the fact by the continual displaying of the signal A. Afterwaiting a reasonable length of time she will remove the calling-plug,thus switching into the circuit again her head-phone, and inform thecalling subscriber X that she cannot get Y.

By the arrangement of circuits shown in Fig. 4 it is impossible for theoperator to listen in on the circuit without removing the calling-plugand cutting off conversation between the connected subscribers. Thisinsures absolute secrecy to the subscriber; but should it be desired toprovide means for the operator to listen in on the circuit a switch orkey K can be provided within her reach for connecting the strand [L3with her receiver.

A switch Z is inserted in line W which can be opened and closed by theoperator, as desired. By means of this simple switch device if theoperator should desire to hold off the ringing-machine until some timeafter the connecting-plug is inserted it is only necessary to open theswitch Z during that time. This delay may be desired by an operator incase of an especially-urgent call, in which case though the wanted linewas found busy the connecting-plug would be inserted and theanswering-plug withdrawn until the supervisory signal associated withthe connectingplug was displayed, when the answering-plug would bereinserted in the jack of the callingline and the switch Z-closed. Bythe samedevice the machine may be started again after it hasautomatically come to a stop, as hereinbefore described, for theoperator need only to open for a moment the switch Z thereby releasingthe locking-relay N", opening contact 21, and closing contact 20 andthen closing the switch again, thus restoring the cir-.

without removing the plug it is only necessary to provide a switch bywhich the circuit to the coil N may be opened, preferably by abutton-switch shunting the coil of the relay N, thus opening for amoment 'by a single pressure of the button the contact and releasing thearmature of the relay N, closing the contact in the circuit through themagnet N, and starting again the ringing mechanism R, or, as explainedabove, the switch Z may be employed.

In Figs. 5 and 6 the ringing mechanism is shown on an enlarged scale intwo views. The mechanism is controlled entirely by the magnet N startingwhen current is switched onto the coil of the magnet N and stopping whencurrent is cut off from it.

S is a shaft made to continuously turn with the uniform slow movement inthe direction of the arrow.

S is a gear-wheel with small teeth on its periphery keyed to shaft S,hence moving with it.

S is a fixed point attached to the frame of the switchboard and uponwhich is fulcrumed a lever having two arms or forks S S Below the pin isa single arm S, which is actuated by the electrom'agnet N. Between thetwo prongs S S of the fork is a shaft or pin S, which is free to turn onits axis. Upon the pin S is mounted a gear-wheel S adapted tointermittently engage with the gear S when moved transversely toward itsufficiently to permit the gear to engage therein. A'pulley S is rigidlyattached to the gear-wheel S and is controlled by a cord S", passingover a pulley and held under tension by the weight W". A stop S isrigidly attached to the pulley S and .rests normally against a rubbercushion S, the cushion forming the terminal of the lower end of a fixedstrip S and thus insulating the stop from the strip. A camwheel S isalso rigidly fixed to the same shaft S, and therefore turns with it.Upon the periphery of the cam-wheel are raised projections 8 ssay five.

S is a stop against which the lower end of the fork, which is of iron,normally rests.

The core of'the electromagnet N when magcontrolled by a spring S.

netized by-the current attracts S to it, thereby swinging the upper endof the fork carrying the wheel S, the pulley-wheel S". the camwheel Suntil the teeth of the wheel :S engage with the teeth of S, compellingthe pulley-wheel and cam to revolve inthe direction of the arrow of thecam. This carries the stop S around to the position shown in dottedlines at S, where the end of the stop comes in contact with the fixedrod S and by virtue of the cord S raises the weightVV. It is plain thaton releasing the wheel S from the wheel S" the pull'of the weightwill-rotate the wheel S and cam-wheel S in acontrary direction back tothe position where it is shown in the drawings. Pivoted at S is anotherrod, S", the upper end of which is The rod being of metal, it can makean electrical contact with the strip S at 22. The lower end of the rod Scarries a plug 8 which is made of metal, but is insulated, as shown inthe drawings, from the rod S. This plug is adapted to cut off anyelectrical contact with the projections of the cam-wheel S. The extremelower end of the rod S also makes a contact, as 23', withone pole ofgenerator C As the rod S oscillates contact 22 is broken just before 23is made, oscillation being compelled, as already stated, by theprojections on the camwheel S When contact 23 is made,- it sends thecurrent of the ringing-generator to the pivot 8 which is connected withthestrand 7?, which connects the tip it of the connecting-plug H, andtherefore when the raised portions-of the cam S are brought far enoughto the left by the pullof the magnet N to engage with the projections son the swinging arm S during the revolution of the gearwheel S contactis made five times at 23 and broken as many times at 22; but during theintervals when the intermediate portions of the cam betweenthe raisedprojections s s are passing the pieces contact at 22 is remade andbroken at 23. During the time con-tact is made at23 the current from thegenerator C is sent out over the line through the tip-strand of the cordand the tip of the plug H. which at that time is inserted in the jack ofthat line. Should the current in the coil of the electromagnet N be cutofi during the partial revolution of the wheel- S, the armature S willbe released and the gear S by reason of the weight W, will be freed fromwheel S and will revolve backwardly until the stop S comes into contactwith the rubber-cushion S Should the wheels remain in mesh until thestop S had turned around to the position shown by the dotted lines at S,it will be in electrical contact with the rod S and willserve tocompletea circuit therefrom to ground through the wheel S axis or shaftS, fork S and wire S, which will cause the supervisory relay l 2 tooperate and in turn permit the system of relays to open the circuitsupplying current i the plug.

and importance and intend to broadly claim to magnet N thus releasingthe gear S and permitting it to revolve back to its normal position, asbefore. Should the calling subscriber remove his receiver from its hookduring the time the generator is in the line, at which time the swingingarm S is lifted by one of the raised portions of the cam S, the relay Nwill remain inactive until a lower portion of the cam is reached by thelever, when it will immediately come into action by the making of thecontact at 22 and the closed circuit at the instrument, whereupon themechanism'will be restored, as before.

By means of the five projections s s on the cam-wheel S five periodicrings will be made; but it is obvious that four, six, or any othernumber desired may be made or that they may be varied, as a series ofvery short rings,

then a silence, then a repetition of the series of short rings. Should areceiver be taken off its hook while the depressed portion of the cam isopposite the piece 8 the mechanism will be restored at once. Such aringing device I term a periodic calling device, as distinguished fromone adapted to ring the subscribers bell continuously or one to ring itcontinuously for a certain length of time. It possesses many advantagesover these latter. The continuous ringer is exceedingly annoying, whilethe single ringer often fails to give sufficient notice; but theperiodic ringer with a time-limit apparatus answers all requirements.Commutators on the generator-shaft have been employed for breaking thecall up into short rings; but these are objectionable in that a fewseconds of time are liable to be lost before the subscribers bell ringsafter the calling-plug is inserted in case the open-circuit part of thecommutator is connected with the circuit at that time. With the rapidityof work now required in an eX- change time even to the fraction of asecond is precious and cannot afford to be lost. My invention preventssuch loss of time and permits the use of a periodic ringer by connectingthe generator with the line and operating the bell immediately upon theinsertion of This feature I consider of value the same.

The supervisory relays shown in Fig. 4-. are not by themselves claimedin this application, but are shown and described and generically andspecifically claimed in my divisionalapplication, Serial No. 95,155.filed February 24, 1902, before referred to, which is being withheld forthe purpose of interference. In this application I intend to claim theother features of the invention.

No general description of the mode of op eration as a whole is needed.It is obvious that many details can be altered Without departing from myinvention or varying its principle. Hence I do not wish to confinemyself to exactdetails as shown.

What I claim is- 1. The combination with a pair of telephonelines andmeans at the central office for uniting them, of a source ofringing-current and a ringing device for applying the same to the calledline, an automatic time-limit apparatus to interrupt the circuit of saidsource of ringing-current after a predetermined time, and meanscontrolled through the agency of a switch at one of the substations ofthe united lines for disconnecting the source of ringingcurrent,substantially as described.

2. The combination with a pair of telephonelines and means at thecentral ofiice for uniting them, of a source of ringing-current and anautomatic ringing device for applying the same to the called line, anautomatic timelimit apparatus to interrupt the circuit of said source ofringing-current after a predetermined time, and means controlled throughthe agency of a switch at one of the substations of the united lines fordisconnecting the source of ringing-current, substantially as described.

3. In a telephone system, the combination with telephone-lines, ofoperators connective means at the central oflice to connect said linesfor conversation, a source of ringing-current, an automatic ringingdevice to connect the said generator to the called line, an automatictime-limit apparatus to disconnect said ringing-generator after apredetermined time, and means for automatically disconnecting saidsource when the called subscriber answers, substantially as described.

4. In a telephone system. the combination with subscribersline-circuits, of a central office at which said lines terminate,operators connective means at the central otfice to connect saidcircuits in pairs for conversational purposes, a calling deviceintroduced into one of said circuits by the act of connecting said meansthereto, an automatic time-limit apparatus for cutting off said deviceafter a predetermined time, and an automatic cut-off device operativeduring said predetermined time by the response of the called subscriberto cut off said calling device, substantially as described.

5. The combination with a pair of telephonelines, of a cord-circuit foruniting them, a source of ringing-current and an automatic deviceadapted to connect said source with the called line, a relay associatedwith said cordcircuit and adapted to respond to current flowing from aportion of the talking-circuit thereof, said relay when energized beingadapted to disconnect said source of ringing-current from the calledline, and an automatic timelimit apparatus for interrupting the flow ofringing-current after a predetermined time, substantially as described.

6. In a telephone system, a telephone-line, operators connective means,a calling-generator adapted to be connected with the line when aconnection is established therewith, a

relay for disconnecting said generator adapted to be operated over thetelephone-line when the called subscriber responds and a time-limitapparatus adapted to close another circuit through said relay after apredetermined time to disconnect said generator.

7 In a telephone system, a telephone-line, operators connective means, acalling-generator adapted to be connected with the line by the act ofconnecting said means therewith, a relay for disconnecting saidgenerator adapted to be operated over the telephone-line when the calledsubscriber responds and a time-limit apparatus adapted to close anothercircuit through said relay after a predetermined time to disconnect saidgenerator, substantially as described.

8. The combination with apair of telephonelines and means at the centralofiice for uniting them, of asource of ringing-current and a ringingdevice for applying the same to the called line, means controlledthrough the agency of a switch at the called station for disconnectingthe source of ringing-current, an automatic time-limit apparatus tointerrupt the flow of ringing-current to said line after a predeterminedtime, and a supervisory signal associated with the called line toindicate the condition of said line, substantially as described.

9. The combination with a pair of telephonelines and means at thecentral office for uniting them, of a source of ringing-current and anautomatic ringing device for applying the same to the called line, meanscontrolled through the agency of a switch at the called station fordisconnecting the source of ringing-current, an automatic time-limitapparatus to interrupt the How of ringing-current to said line after apredetermined time, and a supervisory signal associated with the calledline to indicate the condition of said line, substantially as described.

10. The combination with a pair of telephone-lines, and a cord-circuitat the central office for uniting them, of a central source of currentassociated with the cord-circuit, a supervisory relay associated withthe calling end of the cord-circuit and a signal controlled thereby,said relay being adapted to respond to current in the cord circuit, asource of ringing-current and an automaticdevice for connecting the samewith the called line, a switch at the called substation to permit theflow of current in the line to actuate said relay to disconnect saidsource of ringing-current, and a time-limit apparatus to interrupt theflow of the ringing current after a predetermined time, substantially asdescribed.

11. The combination with a pair of telephone-lines, of an operatorscord-connector at the central office to unite said lines forconversational purposes, a central source of current associated withsaid cord-circuit and lines and adapted to send current over the linesfor talking purposes, supervisory relays and signals associated with theanswering and calling ends of said cord -circuit, the said relays beingadapted to respond respectively to current in the corresponding ends ofthe cord-circuit, a source of ringing-current and an automatic devicefor connecting the same with the called line upon the connection of thecord-circuit therewith, an automatic time-limit apparatus at the centraloffice to interrupt the flow of current from said source ofringing-current after .a predetermined time, and means controlled by thesupervisory rclay associated with the called line and the switch at thecalled substation for disconnecting said ringing source during saidpredetermined time, substantially as described.

12. The combination with a pair of telephone-lines, of an operatorscord-connector at the central otfice to unite said lines forconversational purposes, a central source of current associated withsaid cord-circuit and lines and adapted to send current over the linesfor talk ing purposes, supervisory relays and signals associated withthe answering and calling ends of said cord-circuit, the said relaysbeing adapted to respond respectively to current in the correspondingends of the cord-circuit, a source of ringing-current and an automaticdevice for connecting the same with the called line, upon the connectionof the cord-circuit therewith, an automatic time-limit apparatus at thecentral ofiice to interrupt the flow of current from said source ofringing-current after a predetermined time, and means controlled by oneof the said supervisory relays together with the switch at thecorresponding substation for disconnecting said ringing source,substantially as described.

13. The combination with a telephone-line, of an operators plug, aringing-generator adapted to be connected with the line when the plug isconnected therewith, means for automatically disconnecting saidgenerator within a predetermined time, and further means for againconnecting it with the line without the withdrawal of the plug,substantially as described.

14. The combination with a telephone-line, of an operators plug, aringing-generator adapted to be connected with the line by the act ofconnecting the plug therewith, means for automatically disconnectingsaid generator within apredetermined time, and further means for againconnecting it with the line without the withdrawal of the plug,substantially as described.

15. In a telephone system, the combination with subscribers lines, of acentral oflice at which such lines terminate, operators connective meansat the central office to connect said lines in pairs for conversationalpurposes, an operators telephone introduced into said connective meansby the act of connecting means to cut off said operators telephone andintroduce the said device into the other line of the pair by the act ofconnecting said connective means therewith, substantially as described.

16. In atelephone system, the combination with subscribers lines, of acentral ofiice at which said lines terminate, operators connective meansat the central office to connect said lines in pairs for conversationalpurposes, an operators telephone and a calling device, means tointroduce said telephone into said connective means and thereby into oneof the lines of a pair by the act of connecting said connective meansthereto and for cutting oif said telephone and introducing the callingdevice into the other of said lines by the act of connecting said meanstherewith, and means for cutting ofl" said calling device after apredetermined time, substantially as described.

17. In a telephone system, the combination with subscribers lines, of acentral office at which said lines terminate, operators connective meansat the central office to connect said lines in pairs for conversationalpurposes, an operators telephone and a calling device, means tointroduce said telephone into one of the lines of a pair by the act ofconnecting said connective means thereto and for cutting off saidtelephone and introducing the calling device into the other of saidlines by the act of connecting said means therewith, an auto matictime-limit apparatus for cutting ofl? said device after a predeterminedtime, and an automatic cut-ofi device operative during saidpredetermined time by the response of the subscriber to cut off saidcalling device and time limit apparatus, substantially as described.

18. In a telephone system, the combination with subscribersline-circuits, of a central ofice at which said lines terminate, anoperators cord-circuit at the central office having an answering and aconnecting plug, an operators telephone, means to automatically connectsaid telephone with the cord-circuit upon the insertion of theanswering-plug into a calling-subscribers line, a calling device,automatic means to disconnect said telephone from and connect saidcalling device to, the cord-circuit upon the insertion of theconnecting-plug into a called-subscribers line, means to cut ofi saiddevice after a predetermined time, and further means to automaticallycut off said calling device upon the response of the subscriber.

19. In a telephone system, the combination with line-circuits, of acentral oflice, operators connective means at the central office toconnect said circuits in pairs for conversational purposes, and aperiodic calling device introduced into one of said circuits by the actof connecting said means thereto, and adapted to immediately andinvariably send ringingcurrent over said line, substantially asdescribed.

-20. In a telephone system, the combination with subscribers lines, of acentral ofiice at which said lines terminate, an operators cordcircuitat the central office to variously connect said lines in pairs forconversational purposes and having a calling-plug, a periodic callingdevice introduced into said cord-circuit by the insertion of thecalling-plug into the subscribers line, said device being adapted toimmediately and invariably send ringing-current over said line, andmeans to automatically disconnect said device from the cord-circuit uponthe response of the called subscriber, substantially as described.

21. In a telephonicsystem, the combination with line-circuits, of acentral office at which a said circuits terminate, operators connective-means at the central office to interconnect the line-circuits in pairsfor conversational purposes, a periodic calling device introduced intoone of said circuits by the act of connecting said means therewith, saiddevice being adapted to immediately and invariably send ringing-currentover said line, and an automatic time-limit apparatus for cutting offsaid calling device after a predetermined time, substantially asdescribed.

22. In a telephone system, the combination with subscribers lines, of acentral ofiice at which said lines terminate, operators connective meansat the central office to interconnect said lines for conversationalpurposes, a periodic calling device introduced into one of said lines bythe act of connecting said means therewith and adapted to immediatelyand invariably send ringing-cnrrent over said line, and means toautomatically disconnect said device when the subscriber responds,substantially as described.

23. In a telephone system, the combination with subscribersline-circuits, of a central office at which said lines terminate,operators connective means at the central ofiice to connect saidcircuits in pairs for conversational purposes, a periodic calling deviceintroduced into one of said circuits by the act of connecting said meansthereto and adapted to immediately and invariably send ringing-currentthereover, an automatic time-limit apparatus for cutting olf said deviceafter a predetermined time, and an automatic cut-off device operativeduring said predetermined time by the response of the called subscriberto cut off said calling device, substantially as described.

24. In atelephone system, the combination with subscribers lines, of acentral oflice at which such lines terminate, operators connective meansat the central office to connect said lines in pairs for conversationalpurposes, an operators telephone introduced into one of the lines by theact of connecting said means thereto, a periodic calling device, andmeans IIO to cut off said operators'tel'ephone and introduce the saiddevice into the other line of the pair by the act of connecting saidconnective means therewith, said device being adapted to immediately andinvariably send ringing-current over said line, substantially asdescribed.

25. In a telephone system, the combination with subscribers lines, of acentral office at which said lines terminate, operators connective meansat the central office to connect said lines in pairs for conversationalpurposes, an operators telephone and a periodic calling device, means tointroduce said telephone into one of the lines of a pair by the act ofconnecting said connective means thereto and for cutting off saidtelephone and introducing the calling device into the other of saidlines by the act of connecting said means therewith, said device beingadapted to immediately and invariably send ringing-current over saidline, and means for cutting oif said calling device after apredetermined time, substantially as described.

26. In a telephone system, the combination with subscribers lines, of acentral office at which said lines terminate, operators connective meansat the central oflice to connect said lines in pairs for conversationalpurposes, an operators telephone and a periodic calling device, means tointroduce said telephone into one of the lines of a pair by the act ofconnecting said connective means thereto and for cutting off saidtelephone and introducing the calling device into the other of saidlines by the act of connecting said means therewith, said device beingadapted to immediately and invariably send ringing-current over saidline, and means to automatically disconnect said calling device by theresponse of the subscriber, substantially as described.

27. In a telephone system, the combination with subscribers lines, of acentral office at which said lines terminate, operators connective meansat the central oflice to connect said lines in pairs for conversationalpurposes, an operators telephone and a periodic calling device, means tointroduce said telephone into one of the lines of a pair by the act ofconnecting said connective means thereto and for cutting off saidtelephone and introducing the calling device into the other of saidlines by the act of connecting said means therewith, said device beingadapted to immediately and invariably send ringing-current over saidline, an automatic time-limit apparatus for cutting 01f said deviceafter a predetermined time, and an automatic cut ofi device operativeduring said predetermined time by the response of the subscriber to cutoff said calling device and time-limit apparatus, substantially asdescribed.

28. In a telephone system, the combination with line-circuits, of acentral oflice at which said circuits terminate, operators connectivemeans at the central oflice to interconnect the line-circuits in pairsfor conversational purposes, a periodic calling device introduced intoone of said circuits by the act of connecting said means therewith, anautomatic timelimit apparatus for cutting off said calling device aftera predetermined time, and a supervisory signal at the central office toindicate the response of the called subscriber, substantially asdescribed. I

29. In a telephone system, the combination with line-circuits, of acentral oflice at which said circuits terminate, operators connectivemeans at the central otfice to interconnect the line-circuits in pairsfor conversational purposes, a periodic calling device introduced intoone of said circuits by the act of connecting said means therewith, saiddevice being adapted to immediately and invariably send ringing-currentover said line, means to automatically disconnect said device when thesubscriber responds, and a supervisory signal associated with theoperators means toindicate the condition of the telephone at the calledsubstation, substantially as described.

30. In a telephone system, the combination with line-circuits, of acentral oflice at which said circuits terminate, operators connectivemeans at the central office to interconnect the line-circuits in pairsfor conversational purposes, a periodic calling device introduced intoone of said circuits by the act of connecting said means therewith, anautomatic timelimit apparatus for cutting off said calling device aftera predetermined time, means operative during such predetermined time toautomatically disconnect said device upon the subscribers response, anda supervisory signal associated with the said operators means toindicate the condition of the telephone at the substation, substantiallyas described.

31. In a telephone system, the combination with a plurality oftelephone-lines, of a cordcircuit at the central ofiice to connect thelines together for conversation, a relay associated with each end of thecord-circuit and independently actuated, one of said relays serving toconnect the operators telephone with the cord-circuit when connection isestablished with the calling subscriber, and the other to disconnect thesaid telephone when connection is established with the calledsubscriber, substantially as described.

32. In a telephone system, the combination with a plurality oftelephone-lines, of a cordcircuit at the central office to connect thelines together for conversation, supervisory relays associated with thecord-circuit and controlling supervisory signals, and an operatorstelephone having its connection with the said cord-circuit controlled bysaid relays, substantially as described.

88. In a telephone system, the combination with telephone-lines, of acord-circuit to es tablish connections for conversation with said lines,an operators telephone associated withthe cord-circuit, asupervisory-signal-controlling electromagnet associated with thecordcircuit, means to connect said telephone with the cord-circuit toenable the operator to converse with a calling subscriber, and meanscontrolled by said electromagnet to automatically disconnect saidtelephone from the cordcircuit during connection with a calledsubscribers line, substantially as described.

34. In a telephone system, the combination with telephone-lines, of acord-circuit to es tablish connections with said lines for conversation,an operators telephone associated with the cord-circuit, asupervisory-signalcontrolling electromagnet also associated with saidcord-circuit, and means controlled by said electromagnet forautomatically connecting said telephone with the cord-circuit whenconnection is established thereby with a telephoneline, substantially asdescribed.

35. In a telephone system, the combination with telephone-lines, of acord-circuit to establish connections with said lines for conversation,a supervisory-signal-controlling electromagnet associated with each endof the cord-circuit and adapted to be independently operated by currentin connection with the respective lines with which the cord-circuit maybe connected, an operators telephone associated with the cord-circuit,and having its connection therewith established by the elec-.

tromagnet associated with the answering end thereof and itsdisconnection therefrom accomplished by the electromagnet associatedwith the calling end,su bstantially as described. 36. In a telephonesystem, the combination with telephone-lines, of a cord-circuit toestablish connections therewith for conversation, a supervisory relayassociated with each end of the cord-circuit actuated in connection withthe line with which connection is established, an operators telephonehaving its circuit completed through alternate contacts of the relayassociated with the answering end of the cord-circuit and normalcontacts of the relay associated with the calling end thereof, wherebythe telephone is normally disconnected from the cord-circuit but whenconnection is established with the calling-line it is connectedtherewith and again disconnected during conversation, substantially asdescribed. Signed by me at Chicago, county of Cook, State of Illinois,this 5th day of May, 1902.

JOHN- G. ROBERTS Witnesses:

ELLA EDLER, ROBERT LEWIS AMES.

